Electron beam columns are used in scanning electron microscopes (SEMs) that image objects and in lithography tools for writing patterns onto semiconductor materials to be used as integrated circuits. Conventional electron beam columns consist of an assembly of components, including lenses, magnets, deflectors, blankers, etc., individually machined out of stainless steel or other alloys and individually assembled, and an electron source.
Alternatively, miniature electron beam columns can be made by using, in part, micro-fabricated lenses, deflectors and blankers. These elements are fabricated in silicon using micro-electromechanical systems (MEMS) fabrication technologies and assembled into components. Each component consists of vertically stacked silicon lenses that are electrically isolated by dielectric spacers, like, for example, glass. The silicon and glass elements have at least one aperture concentric with very other aperture creating a path for the electron beam to transverse. The components are energized to focus, blank, and steer the electron beam.
The maximum beam energy of these miniature columns is determined by electrical breakdown which typically occurs across the exposed surfaces located in the apertures and at the edges of the components. The breakdown potential across these surfaces is lower than predicted based on the thicknesses and material properties of the dielectrics for many reasons including surface contamination, roughness, topography, or ambient conditions like humidity, gas composition, and pressure. The reduced breakdown potential of these components caused by surface breakdown effects limits the ability to operate at high voltages, as needed for analysis tools, and limits reliability at low voltages, as needed in scanning electron microscopes, lithography tools, and other applications.
MEMS and other micro-devices are especially susceptible to surface breakdown. Electric fields can be very large as a result of the small distances (e.g., 0.1–1000 um). The sidewalls are often created by sawing or laser cutting. These processes create rough sidewall surfaces and can cause smearing which can further reduce the breakdown path length. An additional failure is contamination creep whereby contaminants, such as hydrocarbons, are charged and “creep” along the surfaces creating short paths. Creep is also mitigated by increasing the surface paths lengths. Sculpting the insulating sidewalls to increase the breakdown path is not possible with conventional technology because the surfaces are typically less than 500 um long.
Accordingly, a component and method of use thereof is needed with a breakdown potential equal to and preferably greater than the predicted values base based on the bulk material properties. This minimizes column failures due to contamination, ambient, or process induced breakdown events. Accordingly, the column incorporating the component would be able to operate at higher voltages and with improved reliability at lower voltages.